This study will explore whether the benefits of switching to three new antiretroviral agents (zidovudine [ZDV], delaviridine[DLV], plus indinavir [IDV]) are greater than the benefits of maintaining lamivudine (3TC), when adding ZDV plus IDV in 3TC-experienced patients. This investigator-initiated, NIH-sponsored 'A' study is a Phase II, randomized, partially double-blinded, controlled study of indinavir sulfate (IDV) combination therapy to determine the safety, tolerability, immunologic and virologic effects of three treatment regimens. 210 ACTG 306 rollover subjects and 60 non-ACTG 306 subjects are expected to enroll (18 and 2 respectively through UCHSC). All subjects enrolled in ACTG 306 who are not permanently off study drug at the time of closure of ACTG 306 will be eligible to enter this study. Subjects with over 500 RNA copies at screening who received ZDV during ACTG 306 will be assigned to the d4T arm (Arm I), while subjects with over 500 RNA copies at screening who did not receive ZDV during ACTG 306 will be randomized to one of the ZDV arms (Arm II or III). Randomization to the ZDV arms will be stratified by whether mono or combination therapy was received during the first 24 weeks of ACTG 306. After randomization to one of the therapy arms, therapy will be administered in a partially double-blind fashion. In addition to subjects from ACTG 306, subjects not enrolled in ACTG 306 will be accrued to the two ZDV-containing arms (Arms II and III) to ensure adequate power for comparison of these arms.